Spatial Ecology of Gila Monsters in a Subsidized Resource Environment

ABSTRACT

Animal movements are often defined using the home range concept. Consequently, home ranges are determined by temporal, spatial, and individual-level processes. Within the environment, one of the key factors influencing an animal’s range and how it uses the environment is that of resources. Alterations to the environment that affect resource distribution and availability can have profound consequences on an animal’s spatial patterns. One of the best examples of this is that of golf courses. Certain environmental modifications exhibited by some human altered environments can have positive effects on certain wildlife species by altering their movement patterns and foraging efforts. We analyzed data collected from 22 Gila Monsters Heloderma suspectum at a subsidized environment in Arizona from 2007 to 2013 and 15 Gila Monsters from a non-subsidized environment from 2000 to 2002. We performed both kernel density estimation and minimum convex polygons for comparability purposes. After adjusting area estimates for sex, number of fixes, and year, males in the subsidized environment had an average overall area of 13.6 ha while the females had an area of 8.3 ha. In the unsubsidized environment, males had an average overall area of 43.2 ha while females had an area of 23.6 ha. Gila Monsters between the two environments also exhibited seasonal differences, primarily in the dry and monsoon seasons. There were also differences in home range overlap within and between sexes. In the subsidized population, there was very little male-male overlap with only two occurances, more female-female overlap and male-female overlap was increased. Male home ranges often overlapped several female home ranges. This suggests that Gila monster home ranges may be smaller in subsidized resource environments than those of un-subsidized environments due to increases in available resources.

Gila Monsters (Heloderma suspectum) and Human Altered Environments

Animal movements are often defined using the home range concept. Formally defined by William Burk in 1943 as, “that area traversed by the individual in its normal activities of foraging, mating, and caring for young. Occasional sallies outside the area, perhaps exploratory in nature, should not be considered part of the home range”. Consequently, home ranges are determined by temporal, spatial, and individual-level processes. Studying animal HR’s has been of special interest to a wide variety of researchers, including those studying relationships between behavior, age, sex, and spacing patterns, resource distribution as it affects space use, the relationship between metabolic requirements and home range size, and space requirements for purposes of controlling problematic species, conservation, and wildlife management.

Within an animals environment, one of the key factors influencing an animals range and how it uses the environment is that of resources. Alterations to the environment that affect resource distribution and availability can have profound consequences on an animals spatial patterns. Some of the best examples of this are alterations caused by human activities. Historically, human alterations to environments have been percieved as having negative consequences on local wildlife populations. However, certain environmental modifications can have positive effects on various wildlife species. This is seen in the implementation of certain golf courses, and green areas. One of the key consequences of golf courses, especially those placed in desert environments is the water irrigation supplementation and horticulture that comes with them. As a result, this enhances primary productivity which increases the presence of vertebrate animals that take advantage of that increase in productivity. In reptiles, faster growth is often correlated with increases in precipitation and available resources. A Recent study has shown that Gila Monsters Heloderma suspectum inhabiting a golf course in the upland Sonoran of Arizona grew larger and faster than unsubsidized populations.

Gila Monsters occupy the hot desert regions of the Mohave Desert in the extreme southeastern Nevada, south through the Sonoran Desert of Arizona into Sonora and northern Sinaloa, Mexico. Gilas are known to be “widely foraging” animals due to their specialization in feeding on the young and eggs of small vertebrate nests. These characteristics and findings make this species a good candidate for studying the potential alterations to animal home ranges that nutrient subsidized areas such as golf courses may have on animal populations.

Study Site

For the subsidized resource population occupying a human altered environment, spatial data was collected on 22 Gila Monsters, 13 females and 9 males at Stone Canyon Golf Club, located in Pima County, Arizona at the base of the Tortolita Mountains. Stone Canyon is a golf club with an area of approximately 345 hectares, consisting of vegetation that is typical of Sonoran desertscrub habitat of the Arizona uplands. Elevation ranges from 900m-1000m, with the landscape consisting of granite outcrop hills with large boulders throughout, interrupted by watered fairways, ponds and paved cart paths. This golf course possesses a partially urbanized housing development with properties encompassing the perimeter of the course.

Figure 1 | Stone Canyon Golf Club, located in Oro Valley, Arizona on the northern edge of Tucson, Arizona.

For the comparison site, the unsubsidized natural population was represented using spatial data that was collected on 15 Gila Monsters, 6 males, 6 females and 3 sub-adults from 2000-2002 using radio-telemetry at Owl Head Buttes, Arizona. Located in Arizona upland Sonoran Desert approximately 19 km north northeast of Stone Canyon, the Owl Head Buttes study site was an area of approximately 200 hectares, with an elevation range of 800m-900m, and discontinuous southern buttes of rocky outcrops. Owl Head harbors no urbanized development or other human altered environments aside from highly spaced unpaved dirt access roads throughout the surrounding area.

Overall Yearly Home Ranges (MCP)

Summary of home range size.

Table 1 | Pooled overall home ranges of Gila Monsters at Owl Head Buttes and Stone Canyon Golf Club. Both 100% and 95% MCPs were calculated between both populations.

Year	Gila	Sex	Environment	Home_Range_100mcp	N100	Home_Range_95mcp	N95
2000	1	female	nonsubsidized	25.20	42	23.00	38
_	2	male	nonsubsidized	28.70	125	24.50	112
_	3	male	nonsubsidized	82.70	89	68.40	78
_	4	male	nonsubsidized	55.60	80	40.50	73
2001	1	female	nonsubsidized	20.10	26	NA	NA
_	2	male	nonsubsidized	23.50	10	NA	NA
_	3	male	nonsubsidized	60.10	18	NA	NA
_	4	male	nonsubsidized	24.40	21	NA	NA
_	10	male	nonsubsidized	28.50	14	NA	NA
_	11	male	nonsubsidized	10.60	22	NA	NA
_	12	male	nonsubsidized	23.60	7	NA	NA
_	13	female	nonsubsidized	8.90	9	NA	NA
_	15	female	nonsubsidized	13.00	11	NA	NA
_	50	female	nonsubsidized	21.00	11	NA	NA
_	51	female	nonsubsidized	7.10	8	NA	NA
2002	2	male	nonsubsidized	66.20	38	40.00	37
_	4	male	nonsubsidized	73.10	76	55.50	73
_	10	male	nonsubsidized	39.50	111	33.30	105
_	11	male	nonsubsidized	39.30	92	31.90	88
_	12	male	nonsubsidized	49.50	66	41.50	63
_	13	female	nonsubsidized	26.30	101	23.70	96
_	15	female	nonsubsidized	39.20	98	21.30	94
_	17	female	nonsubsidized	47.60	106	29.10	101
_	50	female	nonsubsidized	15.80	68	14.10	66
_	51	female	nonsubsidized	18.50	57	12.40	57
2007	F104	female	subsidized	3.37	18	3.37	19
_	F114	female	subsidized	2.51	8	0.58	7
_	F36	female	subsidized	5.05	20	3.49	19
_	F66	female	subsidized	10.23	22	5.56	20
_	M112	male	subsidized	12.51	13	12.51	12
_	M14	male	subsidized	4.66	15	3.87	14
2008	F104	female	subsidized	4.97	53	3.47	50
_	F114	female	subsidized	11.96	52	9.38	49
_	F135	female	subsidized	4.07	16	1.58	15
_	F137	female	subsidized	5.98	15	5.75	14
_	F36	female	subsidized	9.73	54	7.55	51
_	F66	female	subsidized	11.29	51	9.95	48
_	M119	male	subsidized	25.01	58	20.23	55
2009	F104	female	subsidized	7.45	64	7.25	62
_	F114	female	subsidized	11.46	52	8.28	49
_	F135	female	subsidized	6.21	62	5.47	58
_	F137	female	subsidized	6.09	35	5.68	33
_	F147	female	subsidized	17.90	50	14.04	48
_	F36	female	subsidized	7.48	62	5.83	60
_	F66	female	subsidized	12.20	67	11.01	66
_	M112	female	subsidized	7.89	71	1.73	70
_	M119	male	subsidized	22.62	18	16.37	16
_	M69	male	subsidized	1.91	69	1.91	69
_	F146	female	subsidized	9.94	20	8.49	17
2010	F114	female	subsidized	9.65	44	8.30	41
_	F137	female	subsidized	6.32	45	5.26	42
_	F147	female	subsidized	16.65	36	14.75	34
_	F200	female	subsidized	5.36	34	5.23	33
_	F214	female	subsidized	7.38	27	3.01	25
_	F36	female	subsidized	38.81	50	12.16	47
_	F66	female	subsidized	28.96	52	16.22	49
_	M112	male	subsidized	20.46	26	14.41	24
_	M119	male	subsidized	17.46	31	9.70	29
_	M69	male	subsidized	13.85	30	10.75	28
2011	F114	female	subsidized	5.91	22	3.30	20
_	F137	female	subsidized	4.80	33	4.28	31
_	F147	female	subsidized	19.44	24	12.90	22
_	F200	female	subsidized	8.35	28	7.66	27
_	F214	female	subsidized	6.61	22	5.66	21
_	F252	female	subsidized	3.09	17	1.60	16
_	F36	female	subsidized	11.93	23	10.95	21
_	F66	female	subsidized	5.72	5	0.66	4
_	M14	male	subsidized	4.48	13	3.84	12
_	M215	male	subsidized	11.47	16	11.47	15
_	M255	male	subsidized	5.85	16	5.59	15
2012	F114	female	subsidized	10.17	54	7.15	51
_	F137	female	subsidized	2.06	13	1.36	12
_	F147	female	subsidized	17.64	52	16.75	49
_	F252	female	subsidized	5.19	53	3.63	50
_	F36	female	subsidized	10.34	52	10.30	49
_	M14	male	subsidized	4.42	13	3.77	12
_	M215	male	subsidized	11.04	21	9.85	20
_	M255	male	subsidized	8.21	13	5.39	12
2013	F114	female	subsidized	1.16	7	0.28	6
_	F147	female	subsidized	0.31	6	0.00	5
_	F252	female	subsidized	NA	4	NA	NA
_	F36	female	subsidized	0.13	6	0.00	5

Overall combined 100% MCP means averages across sex

Environment	N	Home_Range_100mcp	sd	se	ci
nonsubsidized	25	33.92000	20.793689	4.1587378	8.583213
subsidized	54	10.46278	6.897586	0.9386426	1.882679

Gila Monster Home Range Sizes at Stone Canyon vs. Owl Head Buttes.

Table 2 | Raw group 100% MCP home range means of Stone Canyon and Owl Head Buttes. Grouped by environment and sex.

Environment	Sex	N	Home_Range_100mcp	sd	se	ci
nonsubsidized	female	11	22.063636	12.287414	3.704795	8.254797
nonsubsidized	male	14	43.235714	21.672372	5.792185	12.513255
subsidized	female	37	9.836757	6.984007	1.148164	2.328584
subsidized	male	17	11.825294	6.706133	1.626476	3.447976

Table 3 | Raw group 95% MCP home range means of raw data of Stone Canyon and Owl Head Buttes. Grouped by environment and sex.

Environment	Sex	N	Home_Range_95mcp	sd	se	ci
nonsubsidized	female	6	20.600000	6.286493	2.5664502	6.597270
nonsubsidized	male	8	41.950000	13.987954	4.9454886	11.694222
subsidized	female	37	7.132432	4.339651	0.7134342	1.446912
subsidized	male	17	9.037059	4.934157	1.1967090	2.536910

Gila Monster Yearly Home Range Shifts of 100% MCPs.

Repeated measures ANOVA for Yearly Home Ranges.

ANOVA Table: 100% MCP

Type III Analysis of Variance Table with Satterthwaite's method
                 Sum Sq Mean Sq NumDF  DenDF F value    Pr(>F)    
Environment      688.97  688.97     1 71.486  8.3567 0.0050859 ** 
Year              31.66   31.66     1 71.627  0.3840 0.5374340    
Sex             1375.22 1375.22     1 24.656 16.6803 0.0004079 ***
N100            1797.13 1797.13     1 54.913 21.7978 1.994e-05 ***
Environment:Sex  445.09  445.09     1 25.582  5.3986 0.0283770 *  
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

ANOVA Table: 95% MCP

Type III Analysis of Variance Table with Satterthwaite's method
                Sum Sq Mean Sq NumDF  DenDF F value    Pr(>F)    
Environment     446.03  446.03     1 61.925 30.2487 7.669e-07 ***
Year             14.03   14.03     1 39.326  0.9515  0.335306    
Sex             426.44  426.44     1 29.915 28.9198 8.086e-06 ***
N100             14.22   14.22     1 39.534  0.9646  0.332015    
Environment:Sex 145.74  145.74     1 30.669  9.8835  0.003687 ** 
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Table 4. Directional means of home range after being adjusted for year, sex and sample size.

Table 4. Directional means of home range after being adjusted for year, sex and sample size.

Environment	Sex	lsmean	SE	df	lower.CL	upper.CL
nonsubsidized	female	23.739759	6.015077	66.85165	11.733125	35.74639
subsidized	female	8.314934	3.281775	46.24553	1.710009	14.91986
nonsubsidized	male	43.412310	6.061028	66.27236	31.312006	55.51261
subsidized	male	13.146356	3.754579	53.70952	5.617946	20.67477

Post-Hoc comparisons between sexes and environment:

$emmeans
Environment = nonsubsidized:
 Sex    emmean   SE   df lower.CL upper.CL
 female  23.59 6.00 66.8    11.60     35.6
 male    43.24 6.05 66.3    31.17     55.3

Environment = subsidized:
 Sex    emmean   SE   df lower.CL upper.CL
 female   8.33 3.23 46.6     1.83     14.8
 male    13.68 3.89 49.2     5.87     21.5

Degrees-of-freedom method: kenward-roger 
Confidence level used: 0.95 

$contrasts
Environment = nonsubsidized:
 contrast      estimate   SE   df t.ratio p.value
 female - male   -19.66 4.86 31.6 -4.044  0.0003 

Environment = subsidized:
 contrast      estimate   SE   df t.ratio p.value
 female - male    -5.36 3.81 31.8 -1.405  0.1697 

Graphical Comparisons of Sex Within Each Environment:

Figure 6 | Pairwise comparisons of home range between sexes within each environment. If red arrows overlap those of others, then there is no significant statistical difference.

$emmeans
Sex = female:
 Environment   emmean   SE   df lower.CL upper.CL
 nonsubsidized  23.59 6.00 66.8    11.60     35.6
 subsidized      8.33 3.23 46.6     1.83     14.8

Sex = male:
 Environment   emmean   SE   df lower.CL upper.CL
 nonsubsidized  43.24 6.05 66.3    31.17     55.3
 subsidized     13.68 3.89 49.2     5.87     21.5

Degrees-of-freedom method: kenward-roger 
Confidence level used: 0.95 

$contrasts
Sex = female:
 contrast                   estimate   SE   df t.ratio p.value
 nonsubsidized - subsidized     15.3 8.31 68.7 1.837   0.0705 

Sex = male:
 contrast                   estimate   SE   df t.ratio p.value
 nonsubsidized - subsidized     29.6 8.69 68.3 3.403   0.0011 

Graphical Comparisons of Sex between the two populations:

Figure 7 | Pairwise comparisons of sex between environments. If red arrows overlap those of others, then there is no significant statistical difference.

At Stone Canyon, male yearly home ranges ranged from 1.91 - 25.1 ha, with a mean of 11.8 ± 1.7 S.E. ha (100% MCP), 9.2 ± 1.3 S.E. Ha (95% MCP). Female home ranges ranged from 2.06 – 38.81 ha and a mean of 9.8 ± 1.1 S.E. ha (100% MCP), 7.1 ± 0.7 S.E. ha (95% MCP). Male Gila Monsters at Owl head Buttes had home ranges that ranged from 10.6 – 82.7 ha with a mean of 43.2 ± 5.7 S.E. ha (100% MCP), 41.9 ± 4.9 S.E. ha (95% MCP). Female home ranges ranged from 7.1 – 47.6 with a mean of 22.0 ± 3.7 S.E. ha (100% MCP), 20.6 ± 2.5 S.E. ha (95% MCP). In the analyses of both populations, year had no effect on home range sizes (F = 0.38, P = 0.54), while there was a detected significant difference in home ranges between the two populations (F = 8.35, P = 0.005), as well as sex (F = 16.68, P = 0.0004). Post-Hoc analyses between sexes indicated that there was a significant difference in male home ranges between the two environments (df = 68.3, P = 0.001). There was a slight difference of female home ranges between the two environments, however it was not statistically significant (df = 68.7, P = 0.07). At stone canyon there was no major difference between male and female home ranges (df = 31.8, P = 0.16) with male home range being only 3% larger than females. Males at Owl Head Buttes had a 65% larger home range than did females, and was statistically significant (df = 31.3, P = 0.0003). Interestingly, males at Stone Canyon had smaller home ranges than did the females at Owl Head Buttes (Table x) When using 95% MCPs, male home ranges reduced by 25% and female range by 31%. At Owl Head Buttes, Gila Monsters showed a similar behavior with male home ranges reduced by 20% and female ranges reduced by 26% using 95% MCPs.

Overall Yearly Home Ranges (KDE)

Home range estimation on the Stone Canyon Gila Monsters using 95% KDEs with href bandwidth produced male home ranges ranging from 14.5 – 55.3 ha with a mean of 35.0 ± 3.3 S.E. ha. Female home ranges ranged from 10.1 – 47.8 ha with a mean of 22.9 ± 1.8 S.E. KDE estimates for male and female home ranges were 96% and 80% larger than MCP estimates. Repeated Measures analysis of KDEs suggested that there was a small significant difference between male and female home ranges at Stone Canyon (F = 5.56, P = 0.009). Year did not have an effect on home ranges (F = 0.57, P = 0.45).

Yearly KDE Home Ranges

Year	Gila	Sex	Environment	Home_Range_95kde	N	Home_Range_50kde	N50
2007	F104	female	subsidized	13.84	18	3.69	15
NA	F36	female	subsidized	16.51	20	4.26	16
NA	F66	female	subsidized	32.31	22	7.86	17
NA	M67	male	subsidized	NA	16	8.97	12
NA	M112	male	subsidized	NA	13	15.42	11
NA	M14	male	subsidized	14.52	15	3.76	12
NA	M67	male	subsidized	35.47	14	8.97	10
2008	F104	female	subsidized	13.22	53	2.61	42
NA	F114	female	subsidized	20.55	52	3.68	38
NA	F135	female	subsidized	11.36	16	2.19	12
NA	F137	female	subsidized	20.51	15	5.61	14
NA	F36	female	subsidized	18.89	54	4.98	41
NA	F66	female	subsidized	39.30	50	9.97	43
NA	M119	male	subsidized	47.65	58	12.18	43
2009	F104	female	subsidized	19.11	64	4.63	14
NA	F114	female	subsidized	20.34	52	4.08	43
NA	F135	female	subsidized	14.43	62	4.43	50
NA	F137	female	subsidized	16.94	35	4.99	32
NA	F147	female	subsidized	39.67	62	9.06	52
NA	F36	female	subsidized	13.96	67	3.20	52
NA	F66	female	subsidized	25.90	71	6.35	69
NA	M112	female	subsidized	NA	18	14.27	17
NA	M119	male	subsidized	49.53	69	12.55	61
NA	M69	male	subsidized	NA	NA	NA	NA
NA	F146	female	subsidized	20.17	43	3.97	31
2010	F114	female	subsidized	21.06	44	6.08	35
NA	F137	female	subsidized	13.24	45	3.33	13
NA	F147	female	subsidized	34.73	36	7.13	28
NA	F200	female	subsidized	20.37	34	4.09	25
NA	F214	female	subsidized	14.97	27	3.56	24
NA	F36	female	subsidized	47.49	50	9.73	37
NA	F66	female	subsidized	47.77	52	7.26	33
NA	M112	male	subsidized	55.25	26	8.60	21
NA	M119	male	subsidized	33.88	31	7.14	22
NA	M69	male	subsidized	37.45	30	10.49	22
NA	F146	female	subsidized	33.84	9	8.39	7
2011	F114	female	subsidized	13.82	22	2.66	17
NA	F137	female	subsidized	12.12	33	2.65	25
NA	F147	female	subsidized	43.80	24	9.66	17
NA	F200	female	subsidized	23.96	28	6.86	26
NA	F214	female	subsidized	23.39	22	5.91	18
NA	F252	female	subsidized	8.55	17	1.94	14
NA	F36	female	subsidized	34.90	23	8.81	20
NA	M14	male	subsidized	20.36	12	5.27	10
NA	M215	male	subsidized	46.26	16	11.74	15
NA	M255	male	subsidized	30.10	16	8.25	15
2012	F114	female	subsidized	21.04	54	5.41	45
NA	F137	female	subsidized	7.87	13	1.24	10
NA	F147	female	subsidized	32.98	52	7.74	36
NA	F252	female	subsidized	10.09	53	1.83	39
NA	F36	female	subsidized	27.59	52	7.67	39
NA	M14	male	subsidized	24.02	13	6.49	10
NA	M215	male	subsidized	28.52	21	7.31	15
NA	M255	male	subsidized	32.03	13	8.27	11

Table | Raw Group 95% KDE home range means of Stone Canyon and Owl Head Buttes. Grouped by environment and sex.

Sex	N	Home_Range_95kde	sd	se	ci
female	36	23.06722	11.19254	1.865424	3.787012
male	14	33.94357	12.24405	3.272359	7.069503

Repeated measures ANOVA for KDE Home Ranges.

Repeated Measure ANOVA for 95% KDE overall home ranges

ANOVA Table for 95% KDE (subsidized)

Type III Analysis of Variance Table with Satterthwaite's method
     Sum Sq Mean Sq NumDF  DenDF F value   Pr(>F)   
Year  33.40   33.40     1 39.996  0.5754 0.452584   
Sex  497.09  497.09     1 17.713  8.5619 0.009133 **
N     21.54   21.54     1 37.466  0.3710 0.546150   
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Repeated Measure ANOVA for 50% KDE overall home ranges

Error in eval(predvars, data, env) : object 'Home_Range_50kde' not found

ANOVA Table for 50% KDE (subsidized)

Table | Directional means of KDE home ranges after being adjusted for year, sex and sample size.

Season	Sex	lsmean	SE	df	lower.CL	upper.CL
Dry	female	19.994371	4.908047	41.49770	10.085978	29.90277
Emergence	female	17.014928	7.237399	42.42000	2.413550	31.61631
Monsoon	female	19.938055	5.254150	40.80049	9.325509	30.55060
Post_Monsoon	female	14.969630	5.291163	41.32600	4.286469	25.65279
Dry	male	43.417018	6.385092	42.14273	30.532673	56.30136
Emergence	male	17.576519	15.469710	43.58838	-13.608952	48.76199
Monsoon	male	31.849802	5.728078	42.22605	20.291905	43.40770
Post_Monsoon	male	2.648851	9.134861	43.32296	-15.769382	21.06708

Seasonal Home Range

Seasonal Home Range.

Home range analysis broken down by five seasons; Emergence, Dry, Monsoon, Post Monsoon. The start of emergence was defined by when movement patterns increased from none/minimal to the start of high activity. Effort was taken to match as closely as possible to the Owl Head Buttes emergence date interval. Monsoon season was adjusted using NOAA climate data. The start of was defined when the mean dew point temperatures of three consecutive days were greater than 55 degrees.

Scaling home range analyses by seasonal estimates reduces the number or locations for each lizard. 100% MCPs were used for seasonal home range analyses to avoid any further reduction of locations for each estimation.

Seasonal home ranges at Stone Canyon varied in size between seasons but did not seem shift (Fig.___), with seasonal home ranges overlapping each other, only expanding or collapsing between seasons. Home range patterns at Stone Canyon did not display the same seasonal variation in home range sizes that was observed at Owl Head Buttes. At Stone Canyon, Gila Monsters had relatively smaller home ranges throughout the year, where the highest inflation of range size was observed during the dry season from an increase in male home ranges, 18.2 ± 5.4 S.E. ha to that of female home range sizes at 10.1 ± 2.4 S.E. ha. Females at Stone Canyon displayed similar home ranges during the monsoon season, 10.6 ± 2.5 S.E. ha. Home range sizes at Owl Head Buttes had a much larger amount of variation across seasons than did those at Stone Canyon. There were still slightly larger ranges observed during the dry season, primarily due to increased home range sizes exhibited by males 29.4 ± 4.7 S.E. ha versus females at 15.6 ± 3.8 S.E. ha. During the monsoon season, there was still yet a large influx of home ranges sizes where female home ranges increased to 22.9 ± 4.0 S.E. ha. For both populations, home ranges during the emergence and post-monsoon seasons were small, marking the beginning and ending of overwintering periods, where minimal movement is observed in both groups.

Analysis indicated that there was an effect of season (df = 3, F = 15.41, P = <0.001) as well as an interaction of environment and season (df = 3, F = 6.84, P = <0.001), indicating that changes in seasonal home ranges sizes varied between each environment. Post-Hoc analyses on the Stone Canyon data set with home range means averaged across sex, suggested that there was no significant difference in home ranges between the emergence (4.32 ± 2.55 S.E. ha) and post-monsoon seasons (5.09 ± 2.07 S.E. ha) nor dry and monsoon (12.23 ± 1.74 S.E. ha and 9.04 ± 1.78 S.E. ha). There was also no significance between emergence and dry/monsoon seasons, but there was a difference between dry and post-monsoon (df = 80.2, P = 0.04). Post-Hoc analyses on the Owl Head Buttes population indicated that there was no significant difference between emergence (3.33 ± 2.24 S.E. ha) and post-monsoon (2.36 ± 2.36 S.E.) nor dry and monsoon (18.86 ± 2.25 S.E. ha and 21.85 ± 2.03 S.E. ha) reflecting the same pattern at Stone Canyon. However, there was a significant difference between emergence and dry/monsoon (df = 69.4, P = <0.0001, and df = 68, P = <0.0001 respectively), as well as post-monsoon and dry/monsoon (df = 78.9, P = <0.0001, and df = 74, P = <0.0001). This shows a rather different pattern than seen at Stone Canyon. Pairwise analyses between the two populations indicated no difference between emergence (df = 87.7, P = 0.76) or post-monsoon (df = 89.4, P = 0.35). Differences in home range sizes between the two populations were between the dry and monsoon seasons (Fig.___). Owl Head home ranges were 58% larger than those at Stone Canyon during the dry season, and 76% larger during the monsoon season.

Table 5 | Group means of seasonal home ranges between Stone Canyon (subsidized) and Owl Head Buttes (non-subsidized). These means are averaged across sex.

Environment	Season	N	Home_Range_100mcp	sd	se	ci
nonsubsidized	Dry	12	23.7166667	12.841682	3.7070742	8.159215
nonsubsidized	Emergence	10	2.8100000	3.121414	0.9870776	2.232925
nonsubsidized	Monsoon	13	23.6538462	9.446482	2.6199828	5.708452
nonsubsidized	Post_Monsoon	11	0.6909091	1.013365	0.3055411	0.680788
subsidized	Dry	17	13.0364706	10.574940	2.5647997	5.437133
subsidized	Emergence	9	2.0977778	1.649566	0.5498555	1.267969
subsidized	Monsoon	18	10.5600000	7.518662	1.7721657	3.738943
subsidized	Post_Monsoon	14	2.9885714	5.044404	1.3481737	2.912552

Type III Analysis of Variance Table with Satterthwaite's method
                    Sum Sq Mean Sq NumDF  DenDF F value    Pr(>F)    
Environment         261.63  261.63     1 26.365  5.8375 0.0229042 *  
Season             2072.56  690.85     3 78.967 15.4143 5.534e-08 ***
Sex                 108.84  108.84     1 29.115  2.4285 0.1299532    
N                   335.38  335.38     1 72.754  7.4829 0.0078202 ** 
Environment:Season  920.94  306.98     3 71.524  6.8493 0.0004028 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Table 6 | Seasonal home range means between Stone Canyon (subsidized) and Owl Head Buttes (non-subsidized) popuations for males and females. These are raw means before being adjusted for environment, season, sex, and sample size.

Environment	Season	Sex	N	Home_Range_100mcp	sd	se	ci
nonsubsidized	Dry	female	5	15.6600000	8.6291946	3.8590932	10.7145603
nonsubsidized	Dry	male	7	29.4714286	12.6476235	4.7803524	11.6971008
nonsubsidized	Emergence	female	5	4.4600000	3.4333657	1.5354478	4.2630866
nonsubsidized	Emergence	male	5	1.1600000	1.8242807	0.8158431	2.2651436
nonsubsidized	Monsoon	female	6	22.9833333	9.8151753	4.0070285	10.3003948
nonsubsidized	Monsoon	male	7	24.2285714	9.8668999	3.7293376	9.1253605
nonsubsidized	Post_Monsoon	female	4	1.4000000	1.4491377	0.7245688	2.3059014
nonsubsidized	Post_Monsoon	male	7	0.2857143	0.3670993	0.1387505	0.3395102
subsidized	Dry	female	11	10.1754545	8.0883118	2.4387178	5.4338018
subsidized	Dry	male	6	18.2816667	13.2661214	5.4158714	13.9219406
subsidized	Emergence	female	6	2.1133333	1.8474920	0.7542354	1.9388239
subsidized	Emergence	male	3	2.0666667	1.5326556	0.8848792	3.8073277
subsidized	Monsoon	female	11	10.6918182	8.4988679	2.5625051	5.7096172
subsidized	Monsoon	male	7	10.3528571	6.3010018	2.3815548	5.8274547
subsidized	Post_Monsoon	female	11	3.6309091	5.5527983	1.6742317	3.7304207
subsidized	Post_Monsoon	male	3	0.6333333	0.8007705	0.4623250	1.9892241

Adjusted Seasonal Means

Post-Hoc comparisons between populations for seasonal home range analysis:

$emmeans
Season = Dry:
 Environment   emmean   SE   df lower.CL upper.CL
 nonsubsidized  18.86 2.25 88.4   14.383    23.34
 subsidized     12.23 1.75 87.4    8.745    15.72

Season = Emergence:
 Environment   emmean   SE   df lower.CL upper.CL
 nonsubsidized   3.33 2.24 88.7   -1.118     7.77
 subsidized      4.32 2.55 84.7   -0.741     9.39

Season = Monsoon:
 Environment   emmean   SE   df lower.CL upper.CL
 nonsubsidized  21.85 2.03 87.5   17.811    25.89
 subsidized      9.04 1.78 86.0    5.515    12.57

Season = Post_Monsoon:
 Environment   emmean   SE   df lower.CL upper.CL
 nonsubsidized   2.36 2.36 87.0   -2.322     7.04
 subsidized      5.09 2.07 85.8    0.981     9.21

Results are averaged over the levels of: Sex 
Degrees-of-freedom method: kenward-roger 
Confidence level used: 0.95 

$contrasts
Season = Dry:
 contrast                   estimate   SE   df t.ratio p.value
 nonsubsidized - subsidized    6.629 2.81 88.3  2.358  0.0206 

Season = Emergence:
 contrast                   estimate   SE   df t.ratio p.value
 nonsubsidized - subsidized   -0.996 3.32 87.7 -0.300  0.7648 

Season = Monsoon:
 contrast                   estimate   SE   df t.ratio p.value
 nonsubsidized - subsidized   12.808 2.66 87.2  4.814  <.0001 

Season = Post_Monsoon:
 contrast                   estimate   SE   df t.ratio p.value
 nonsubsidized - subsidized   -2.734 2.96 89.4 -0.924  0.3581 

Results are averaged over the levels of: Sex 

Graphical Comparisons of seasons between the two populatins:

Figure 11 | Pairwise comparisons of each season between environments. Overlapping red bars indicate no statistical difference.

$emmeans
Environment = nonsubsidized:
 Season       emmean   SE   df lower.CL upper.CL
 Dry           18.86 2.25 88.4   14.383    23.34
 Emergence      3.33 2.24 88.7   -1.118     7.77
 Monsoon       21.85 2.03 87.5   17.811    25.89
 Post_Monsoon   2.36 2.36 87.0   -2.322     7.04

Environment = subsidized:
 Season       emmean   SE   df lower.CL upper.CL
 Dry           12.23 1.75 87.4    8.745    15.72
 Emergence      4.32 2.55 84.7   -0.741     9.39
 Monsoon        9.04 1.78 86.0    5.515    12.57
 Post_Monsoon   5.09 2.07 85.8    0.981     9.21

Results are averaged over the levels of: Sex 
Degrees-of-freedom method: kenward-roger 
Confidence level used: 0.95 

$contrasts
Environment = nonsubsidized:
 contrast                 estimate   SE   df t.ratio p.value
 Dry - Emergence            15.532 3.07 69.4  5.054  <.0001 
 Dry - Monsoon              -2.992 2.89 67.3 -1.036  0.7292 
 Dry - Post_Monsoon         16.500 3.24 78.9  5.098  <.0001 
 Emergence - Monsoon       -18.524 2.91 68.0 -6.361  <.0001 
 Emergence - Post_Monsoon    0.968 3.08 73.0  0.314  0.9891 
 Monsoon - Post_Monsoon     19.492 3.03 74.0  6.426  <.0001 

Environment = subsidized:
 contrast                 estimate   SE   df t.ratio p.value
 Dry - Emergence             7.907 3.11 88.6  2.543  0.0602 
 Dry - Monsoon               3.187 2.28 66.0  1.395  0.5070 
 Dry - Post_Monsoon          7.137 2.68 80.2  2.666  0.0450 
 Emergence - Monsoon        -4.720 3.20 89.6 -1.475  0.4569 
 Emergence - Post_Monsoon   -0.769 2.94 77.2 -0.262  0.9937 
 Monsoon - Post_Monsoon      3.951 2.78 84.9  1.421  0.4899 

Results are averaged over the levels of: Sex 
P value adjustment: tukey method for comparing a family of 4 estimates 

Graphical Comparisons between seasons within the two populations:

Figure 12 | Pairwise comparisons between seasons within each environment against estimated marginal means. Overlapping red bars indicate no statistical difference.

$emmeans
Season = Dry:
 Sex    emmean   SE   df lower.CL upper.CL
 female   6.92 2.19 47.2    2.523     11.3
 male    20.36 2.77 48.3   14.798     25.9

Season = Emergence:
 Sex    emmean   SE   df lower.CL upper.CL
 female   5.00 2.91 45.2   -0.853     10.9
 male     5.63 4.00 49.0   -2.403     13.7

Season = Monsoon:
 Sex    emmean   SE   df lower.CL upper.CL
 female   6.27 2.34 46.2    1.560     11.0
 male    11.39 2.51 48.4    6.354     16.4

Season = Post_Monsoon:
 Sex    emmean   SE   df lower.CL upper.CL
 female   5.94 2.09 47.9    1.738     10.1
 male     3.09 3.99 48.5   -4.937     11.1

Degrees-of-freedom method: kenward-roger 
Confidence level used: 0.95 

$contrasts
Season = Dry:
 contrast      estimate   SE   df t.ratio p.value
 female - male  -13.441 3.68 47.2 -3.653  0.0006 

Season = Emergence:
 contrast      estimate   SE   df t.ratio p.value
 female - male   -0.632 4.73 49.0 -0.134  0.8943 

Season = Monsoon:
 contrast      estimate   SE   df t.ratio p.value
 female - male   -5.121 3.53 47.1 -1.449  0.1539 

Season = Post_Monsoon:
 contrast      estimate   SE   df t.ratio p.value
 female - male    2.847 4.36 48.9  0.652  0.5173 

Graphical Comparisons between sex within the subsidized population:

Table 7 | Mean individual seasonal home ranges pooled from the entire study period. Missing values are depicted where no locations for that animal during that period were successfull.

Seasonal Individual Home Ranges (MCP).

X	Emergence	X.1	X.2	Dry	X.3	Monsoon	X.4	Post.Monsoon	X.5
Lizard	Sex	Area (ha)	N	Area	N	Area	N	Area	N
M69	Male	0.33	4.00	36.73	24.00	14.84	22.00	0.07	8.00
M67	Male	NA	NA	5.71	9.00	7.72	7.00	NA	NA
M255	Male	3.23	7.00	NA	NA	1.07	9.00	NA	NA
M215	Male	2.64	7.00	8.28	11.00	7.22	12.00	NA	NA
M14	Male	NA	NA	6.20	15.00	7.50	10.00	NA	NA
M119	Male	NA	NA	27.84	17.00	19.98	67.00	1.55	9.00
M112	Male	NA	NA	24.93	16.00	14.14	29.00	0.28	8.00
F66	Female	0.33	5.00	9.60	97.00	33.65	79.00	1.36	16.00
F36	Female	2.94	12.00	24.99	99.00	10.30	118.00	19.14	27.00
F252	Female	1.27	8.00	2.54	14.00	6.48	30.00	0.39	9.00
F214	Female	NA	NA	5.04	10.00	7.79	28.00	1.87	9.00
F200	Female	NA	NA	4.71	8.00	4.23	40.00	2.05	12.00
F147	Female	5.44	14.00	25.52	57.00	18.21	70.00	7.14	18.00
F146	Female	NA	NA	9.55	22.00	5.97	17.00	0.03	7.00
F137	Female	1.71	6.00	6.54	43.00	6.95	62.00	2.19	17.00
F135	Female	NA	N	3.71	25.00	5.72	48.00	0.68	5.00
F114	Female	0.99	12.00	13.66	99.00	10.72	84.00	4.56	24.00
F104	Female	NA	NA	6.07	70.00	7.59	49.00	0.53	13.00

Means Overall 1.89 13.04 10.56 2.99
Male 2.07 18.28 10.35 0.63
Female 2.11 10.18 10.69 3.63

$emmeans
Season = Dry:
 Sex    emmean   SE   df lower.CL upper.CL
 female  14.05 3.70 32.3     6.50    21.59
 male    21.97 3.95 32.7    13.93    30.02

Season = Emergence:
 Sex    emmean   SE   df lower.CL upper.CL
 female   4.64 3.10 31.5    -1.68    10.97
 male     1.34 3.24 32.1    -5.25     7.94

Season = Monsoon:
 Sex    emmean   SE   df lower.CL upper.CL
 female  22.14 3.01 31.1    16.00    28.28
 male    20.34 3.24 31.8    13.74    26.95

Season = Post_Monsoon:
 Sex    emmean   SE   df lower.CL upper.CL
 female   2.96 4.76 32.0    -6.74    12.66
 male     2.80 4.35 33.0    -6.05    11.66

Degrees-of-freedom method: kenward-roger 
Confidence level used: 0.95 

$contrasts
Season = Dry:
 contrast      estimate   SE   df t.ratio p.value
 female - male   -7.924 4.39 31.6 -1.803  0.0809 

Season = Emergence:
 contrast      estimate   SE   df t.ratio p.value
 female - male    3.302 4.44 31.6  0.744  0.4622 

Season = Monsoon:
 contrast      estimate   SE   df t.ratio p.value
 female - male    1.799 4.02 30.5  0.447  0.6581 

Season = Post_Monsoon:
 contrast      estimate   SE   df t.ratio p.value
 female - male    0.154 4.46 31.9  0.035  0.9726 

Graphical Comparisons between sex within the non-subsidized population:

Seasonal Home Range (KDE)

Table | Raw KDE group means of seasonal home ranges between sexes at Stone Canyon (subsidized).

Error in summarySE(season.kde, measurevar = "Home_Range_95kde", groupvars = c("Season",  : 
  could not find function "summarySE"

Error in summarySE(season.kde, measurevar = "Home_Range_95kde", groupvars = c("Season"),  : 
  could not find function "summarySE"

ANOVA Table. Seasonal KDE

Type III Analysis of Variance Table with Satterthwaite's method
            Sum Sq Mean Sq NumDF  DenDF F value   Pr(>F)   
Season     2654.14  884.71     3 39.026  4.5184 0.008181 **
Sex         179.65  179.65     1 25.426  0.9175 0.347144   
N            66.05   66.05     1 33.912  0.3373 0.565207   
Season:Sex 1743.14  581.05     3 36.391  2.9675 0.044584 * 
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Raw Seasonal KDE Means

Adjusted Seasonal KDE Means

$emmeans
Season = Dry:
 Sex    emmean    SE   df lower.CL upper.CL
 female  19.99  4.91 41.5    10.09     29.9
 male    43.42  6.39 42.1    30.53     56.3

Season = Emergence:
 Sex    emmean    SE   df lower.CL upper.CL
 female  17.01  7.24 42.4     2.41     31.6
 male    17.58 15.47 43.6   -13.61     48.8

Season = Monsoon:
 Sex    emmean    SE   df lower.CL upper.CL
 female  19.94  5.25 40.8     9.33     30.6
 male    31.85  5.73 42.2    20.29     43.4

Season = Post_Monsoon:
 Sex    emmean    SE   df lower.CL upper.CL
 female  14.97  5.29 41.3     4.29     25.7
 male     2.65  9.13 43.3   -15.77     21.1

Degrees-of-freedom method: kenward-roger 
Confidence level used: 0.95 

$contrasts
Season = Dry:
 contrast      estimate    SE   df t.ratio p.value
 female - male  -23.423  8.47 41.2 -2.765  0.0085 

Season = Emergence:
 contrast      estimate    SE   df t.ratio p.value
 female - male   -0.562 16.72 43.7 -0.034  0.9734 

Season = Monsoon:
 contrast      estimate    SE   df t.ratio p.value
 female - male  -11.912  8.07 41.2 -1.475  0.1477 

Season = Post_Monsoon:
 contrast      estimate    SE   df t.ratio p.value
 female - male   12.321 10.14 43.9  1.215  0.2308 

Home Range Overlap (MCP)

Gila Monster Home Range Overlap of 100% MCPs.

Figure 13 | Interactive map: Home Range overlap by sex of 100% MCPs at Stone Canyon. Red polygons represent female lizards, and blue represents male lizards.

The Stone Canyon population seems to exhibit greater female-female overlap as well as considerable overlap of male-female home ranges. There appears to be limited male-male overlap, with occurance happening in only two male-male home range polygons. This finding is in contrast to the Owl Head buttes study which revealed that there was a large degree of overlap among male-female and male-male overlaps (Table x). Gillardo concluded that, in their study, the high degree of overlap in males-males interactions may be due to having larger home ranges for mate searching activities. Males may have and increased home range size to maximize their access to multiple females. She concluded that the lack of female-female overlap may be due to smaller home range sizes.

At Stone Canyon, males have reduced home range sizes (Table 6; Fig. 4). However, males still retain home range overlap with multiple females while having reduced contact with other males. This may be in response to nutrient subsidies that reduce the need to have expanded home range sizes for foraging activities for both males and females. There may also be a higher density of females as a response to resource availability and reduced range requirements. Males are not forced to expand home ranges for mate searching to the extant that individuals at Owl Head Buttes may be subject to.

Table 8 | Home range overlap of Gila Monsters at the nutrient subsidized site. Male-male overlaps only occured between two pairs of males: M14-M69 and M119-M215 at 0.5 ha. and 19.5 ha. respectively and were therefore not included in the table.

Table: Home range overlap of Stone Canyon Gila Monsters using 100% MCPs.

ID              F36          F66    F104   F135   F137   F146   F147   X             M14           M67    M69    M112    M119    M215    M255 
--------------  -----------  -----  -----  -----  -----  -----  -----  ------------  ------------  -----  -----  ------  ------  ------  -----
Female:Female                                                          Male:Female                                                            
F36             _            5.13   _      _      _      4.65   _                    _             _      _      _       19.44   18.51   _    
F66             5.13         _      _      _      _      5.05   _                    _             _      2.6    _       _       _       _    
F104            _            _      _      0.5           _      _                    _             _      _      _       _       _       _    
F114            _            _      _      _      _      _      _                    _             _      _      5.82    _       _       _    
F135            _            _      0.5    _      2.89   _      3.94                 _             _      2.04   _       _       _       _    
F137            _            _      _      2.89   _      _      7.91                 _             _      0.55   _       _       _       _    
F146            4.65         5.05   _      _      _      _      _                    0.14          _      0.76   _       _       _       _    
F147            _            _      _      3.94   7.91   _      _                    3.73          0.21   4.6    _       _       _       _    
F200            _            _      _      _      _      _      _                    _             _      _      6.49    _       _       _    
F252            _            _      _      _      _      _      _                    _             _      _      _       _       _       3.45 
                                                                                                                                              
Mean =          4.3 ± 0.86                                             Mean =        5.26 ± 1.78                                              
                                                                                                                                              
                                                                                                                                              
ID              F36          F66    F104   F135   F137   F146   F147                 M14           M67    M69    M112    M119    M215    M255 
Female:Female                                                          Male:Female                                                            
Net             6.84         7.25   0.5    4.44   7.91   6.77   8.96                 3.87          0.21   8.57   12.31   21.24   20.32   3.45 
Prportion       0.2          0.2    0.1    0.5    1      0.7    0.3                  0.4           0.02   0.5    0.4     0.6     1       0.2  

Home Range Overlap Summary

Interaction	N	OL	sd	se	ci
Female_Female	7	4.295714	2.271694	0.8586198	2.100967
Male_Female	13	5.256923	6.429806	1.7833074	3.885493
Male_Male	4	9.980000	10.958108	5.4790541	17.436795

Home Range Overlap (KDE)

Figure 14 | Interactive map: Home Range overlap by sex of 95% KDEs at Stone Canyon. Red polygons represent female lizards, and blue represents male lizards.